If Sir Ian were not so personally modest, one might call him an "oil baron". However, that would instantly conjure up images of J.R. Ewing and the like.

Sir Ian has decidedly more probity - and thus widespread respect. More Deeside than Dallas.

Wherein lay Mr Salmond's problem today.

Sir Ian had said that the FM had substantially over-estimated the volume and tax value of remaining North Sea reserves. How to respond?

Mr Salmond could not play the man. He could not castigate Sir Ian directly, having earlier praised him in other circumstances.

Commanding respect

But the FM was not stumped. Indeed, despite the conundrum, he was notably assertive. Perhaps I should say "because of" rather than "despite".

Mr Salmond frequently seems to thrive on challenge.

So today he stressed that Sir Ian was a figure who commanded the utmost respect. He did not quite call him "an honourable man". Too Roman.

But he indicated that other views are also available. In particular, he drew upon Professor Alex Kemp of Aberdeen University who has suggested that fields yet to be exploited may enhance the riches of the North Sea still further.

Further, Mr Salmond argued that - even at Sir Ian's estimate - some 15 billion barrels of oil or so was a decent settlement.

Other countries, he said, would surrender their eye teeth for such a dowry.

Resorting to satire, he depicted Scotland as a "poor benighted country", burdened with oil wealth.

Image copyrightBBC news grabImage caption
The main topic of debate in the chamber was inspired by Sir Ian Wood's remarks

Ms Lamont was unimpressed. Scotland was not benighted. Rather it was a "wonderful country" which deserved better from its leaders.

Sir Ian, she implied, had ca'd the feet from the independence argument.

For the Tories, Ruth Davidson piled in too. Mr Salmond, she said, had "twisted facts" and "closed his ears" to the facts of oil production. It was declining, rapidly.

Cue outrage and barracking. As Mr Salmond attempted to answer, Nicola Sturgeon in particular could be discerned, actively heckling the Tory chief.

I heard the word "rubbish" and "you want to talk us down" among the vigorous contribution.

In the chair, Ms Marwick became restless once more. "Settle down", she said, part soothing, mostly strident.

Mr Salmond persisted, recalling that in the 1970s there had been a civil service report which had suggested that, with control of oil, an independent Scotland would have gained untold riches.

Untold, the FM noted, in that the report stayed secret for 30 years.

Which brought those particular exchanges to a close. Leaving no time for Mr Salmond's critics to deliver the familiar argument to the effect that Scotland must deal now with contemporary circumstances in the North Sea and elsewhere.